New migration maps serve as tools to help big game in West
CHEYENNE, Wyo. — The life-or-death journey made by mule deer during the second- longest big game migration in North America came down to their ability to squeeze through a fence — a discovery made by scientists using wildlife GPS tracking techniques to map animal migrations in the West in unprecedented detail.
The resulting atlas of migration corridors in Arizona, Idaho, Montana, Nevada, Utah and Wyoming published by the U.S. Geological Survey can help elk, mule deer, antelope and other animals by focusing efforts to reduce man-made obstacles along their journeys, biologists and wildlife advocates say.
“The new technology, the GPS collars and the computer programs that are able to analyze this data, is giving us such a different picture of what migrating wildlife do,” said Miles Moretti, president of the Salt Lake City-based Mule Deer Foundation, which funded some of the research. “This has given us some information like we’ve never had before, which will also now in turn drive the policy.”
A former wildlife biologist, Moretti used to venture into the field every couple weeks to locate animals fitted with radio collars. These days scientists can follow animals from their computers in almost real time, gathering vastly more data with a lot less trouble.
They watch as big game animals in the West chase emerging spring greenery to ever- higher elevations, then return to lowlands to avoid the worst of winter’s cold and snow. Some mavericks meander off on their own squiggly computer lines. Most follow the crowd — or literally the herd — on migration corridors, a kind of highway for animals.
“The big highways, a lot of the herd is using. Once you identify those, that becomes an important target for conservation,” said Matthew Kauffman, USGS lead scientist for the mapping project.
Human development — homes, roads, fences, oil and gas fields and mining operations — increasingly interferes with Western migrations, sometimes with little awareness of what’s at stake for animals cherished by wildlife watchers and hunters alike.
Mule deer, for example, plummeted in number when home development surged in the Wyoming ski enclave of Jackson Hole decades ago, said Mike Eastman, a writer and wildlife photographer who grew up in the area and used to guide hunters there.
“Mule deer are real susceptible to a lot of people in an area, and it just kind of pinches them off,” Eastman said. “They’re kind of like steelhead or salmon and can’t get up there because a dam is in the way.”
Fences that impede mule deer — big- eared cousins of whitetail deer — or pronghorn antelope can be deadly. Roads, such as Interstate 80 from Wyoming to California, also hold up and kill migrating big game animals.
While some animals, such as migratory birds, can genetically inherit knowledge about when and where to migrate, others learn from their elders. Reintroduced populations of Western big game animals need decades to rediscover migration routes, research suggests.
Even so, remarkable migrations persisit in the West.
Over the past decade, Kauffman and others have used GPS to map migrations including the second-longest known in North America, a 300- mile round- trip journey mule deer make each year between a desert and high mountain ranges in western Wyoming.
The science- guided conservation projects included the $2.1 million purchase of half a square mile of land earmarked for home development near Pinedale, Wyoming. The 2015 purchase with public and private funds helped ensure that 5,000 mule deer can continue to pass through a migration “bottleneck” where the town and a lake narrow the path of the animals.